Remember, the World Cup is still a few months away so there is plenty of time for Terry's form - or anybody else's - to dip or rise.

The good news for Ferdinand, the new England captain, is that he is now showing signs of progress after his injury worries. That is also good news for Terry, who, when he is playing for England, relies on his understanding with the Manchester United defender.

Terry might be accused of lacking pace sometimes, but he is a top-class international and, as I will explain, the England starting XI would be weaker without him.

Should events conspire to eliminate either Terry or Ferdinand prior to Fabio Capello's squad announcement on 16 May, I still think the England boss has some very able deputies to cover any gaps.

THE CONTENDERS

Terry, 29, and Ferdinand, 31, have had a few injuries in their careers and are at stage now where they are beginning to creak a bit.

But what they lack in speed they make up in other areas, such as their reading of the game and their experience. The pair have 135 caps between them and, when they play side-by-side, are greater than the sum of their parts.

But what happens when either one of them is injured?

TERRY AND FERDINAND THIS SEASON

30 - League appearances - 9

13 ----- Clean sheets ----- 4

2 ---------- Goals ---------- 0

59 - Total England caps - 76

Since Capello took charge at the start of 2008, Matthew Upson has often been the man to deputise. It helps that, at 30, the West Ham defender has the know-how to defend on the international stage.

I know Matty quite well from when he was at Arsenal. At the time, it bothered him a lot that he was not getting enough opportunities. He thought he should be playing because he was young and he was keen, but he ended up learning his trade elsewhere and he's looked solid for England so far.

I think he knows that he is the go-to man should anything happen to Terry or Ferdinand - and that's a good position for him to be in. It gives him something to aim at.

Joleon Lescott would be next in line barring any injury problems but he looks touch and go now. I think the move from Everton to Manchester City has affected him in some way because his form this season has not been brilliant. He's had to fuse a new partnership with Kolo Toure and he still has quite a bit to do to be pushing Upson for that third-choice spot with England.

Stoke's Ryan Shawcross is the other contender, having been selected for the squad to face Egypt earlier this month.

UPSON AND LESCOTT THIS SEASON

25 - League appearances - 18

7 ------- Clean sheets ------- 4

3 ----------- Goals ----------- 1

19 --- Total England caps --- 9

He caught the eye of both me and Match of the Day colleague Alan Hansen earlier in the season. We both like him. I believe he is disciplined in the way he leads his life, so it appears he has a lot of the right attributes.

He seems like he wants to learn, and he has bounced back well after the bad press he got after the challenge that broke Aaron Ramsey's leg. I think he has a chance of going to South Africa.

It's a shame there is still a question mark over Ledley King's fitness. He has been playing for Spurs, but is he fit enough to play two games in quick succession? That said, I believe Capello has shown a lot of interest in him and has been in touch with Tottenham to find out how he is progressing each week.

STRENGTHS AND WEAKNESSES

As players get older, their weaknesses get highlighted. That's only natural as Father Time catches up with them.

Terry has never been the quickest - he's not bad in a straight line but sometimes can get caught out when the ball is played around the corner and into the channel - but he still reads the game really well. That's the one thing about him that stands out.

Ferdinand is similar in this respect. So whenever either Terry or Ferdinand are in trouble, the other one should be able to read the situation and offer cover.

I was playing in a back four at Arsenal until I was 38. Nigel Winterburn was 37 and Tony Adams was 36, so we had to learn to look out for each other.

SHAWCROSS AND KING THIS SEASON

24 - League appearances - 15

8 ------ Clean sheets ------ 6

2 ---------- Goals ---------- 1

0 -- Total England caps -- 19

That kind of understanding only comes with playing with the same players over a long period of time and learning each other's game. That is why having Upson as the regular first-choice stand-in is a benefit. He should know how his England team-mates operate.

Upson is like Terry in that he can get caught out by those passes down the channel after the striker has made him spin around. But his defensive team-mates should be able to cover him.

As for Terry, he has the ability to anticipate situations before they happen. I don't think there is anyone better at being in the right position in the box on a consistent basis.

Watch him for Chelsea and count the number of times he is there to meet the ball as it comes in from a wide area. Many people might think the opposition player has been guilty of a bad cross, but it's more to do with Terry being in the right place.

Tony Adams was the same. He used to get in the correct position in the box regardless of who he was marking and would generally be where the forward wanted to be anyway.

It's the same at the attacking end, too. Terry can anticipate where the ball is going to come from on set-pieces. When he attacks it, there are not many people who will stop him getting there.

Ferdinand is more comfortable with the ball on the deck, so he complements Terry well. Judging by Sunday's win over Liverpool, it looks like Ferdinand and Manchester United team-mate Nemanja Vidic are beginning to form a good partnership again, too.

VERDICT

If the World Cup was next week, Capello might be a worried man as far as the centre-back position is concerned. But it's not and both Terry and Ferdinand are fit and playing well.

I'd take those two to South Africa, plus Upson and Lescott. Shawcross and King are the outsiders but Capello might have some masterplan up his sleeve to use King for the odd game if he is fit.

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